TCA9555: Does this part act as a buffer and a switch?

Lauren Mayfield

Part Number: TCA9555
Other Parts Discussed in Thread: TCA9543A

Hi team,

Asking this Q on behalf of my customer-

One of the I2C busses that I am switching to is off my board (connecting to it through cable). Therefore, I am considering putting in an I2C buffer after the TCA9555.

My question is: does the TCA9555 act as both a buffer and an I2C switch?

Or, is it only an I2C switch? I am asking, because if it also acts as a buffer, if I add another buffer afterwards, that buffer will be redundant.

Thanks,
Lauren

over 5 years ago

0 Ravi Singh over 5 years ago

TI__Mastermind 22965 points

Hi Lauren,

Can you double check the part number?

The TCA9555 is an IO expander device (not a I2C switch or a buffer).

0 Lauren Mayfield over 5 years ago in reply to Ravi Singh

TI__Expert 8035 points

Hi Ravi, thank you for catching that. It is the TCA9543A, not the TCA9555.

0 Danny Bacic over 5 years ago in reply to Lauren Mayfield

TI__Mastermind 26836 points

Hello Lauren,

The TCA9543A acts only as a switch. The two sides of the bus on any given channel are connected across a pass-gate transistor. For example, here is SC0/SD0:

You can also check out sections 9.2 and 9.2.2 of the TCA9543A datasheet for some great design guidelines. Here, it will also note that "if both channels [of the switch] will be activated simultaneously, each of the slaves on both channels will contribute to total bus capacitance."

Please let me know if there are any other questions I can help with!

Best,

Danny

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TCA9555: Does this part act as a buffer and a switch?